Linear slides are widely used to allow linear translational motion between members of mechanisms. These linear slides typically include adjustment elements for controlling clearances between the inner member and its guides. The adjustment elements are often used to apply a preload force to eliminate backlash and reduce compliance perpendicular to the direction of articulation. In the majority of these arrangements, compressive loading of the bearing elements between the outer member and inner member is provided by manual adjustment.
It is desirable to eliminate the need for continued adjustment in applications where the linear slides are not readily accessible or where frequent adjustment would otherwise be required due to the wear of constant use. Continued adjustment has the disadvantage that the adjustments may not be uniform in application or may be too tight or too loose. If done manually adjustment has the additional disadvantage of being labor intensive and therefore expensive. Even a linear slide that is properly adjusted when free standing can, when installed, become too loose or become too tight to the point of binding, depending on the exact interface conditions of the installation.
One previous arrangement, disclosed in U.S. Pat. No. 3,145,065, provides a compensating mechanism to prevent loss of accuracy in a rectilinear bearing assembly using balls and radially compliant longitudinal rods to support and guide the inner member within the outer member. The longitudinal rods are comprised of tubular members having a relatively large modulus of elasticity and a relatively high yield point. These tubular members are meant to compensate for loose tolerances in the ball assembly.
Another arrangement, disclosed in U.S. Pat. No. 2,028,718, provides ball races formed by elastic steel bands in order to form a dust proof bearing. These steel bands are meant to reduce the need for accuracy in manufacture of the bearing since these bands tend to compensate for ball expansion.
Another arrangement, disclosed in the British patent specification 703,762, discloses apparatus for providing an automatic non-manual adjustment of a linear slide by applying the pressure of a spring against a bar supporting a linear slide mechanism. This however is a pre-use adjustment and the bar coupling the spring pressure to the linear slide is bolted down prior to use of the linear slide bearing. Hence, the adjustment is static and the linear slide bearing may subsequently come out of adjustment during use.
These priorly disclosed mechanisms do not however provide continuous compensation for changes occurring after an initial adjustment.